Goniometer-based body-tracking device and method

ABSTRACT

A sensing system is provided for measuring various joints of a human body for applications for performance animation, biomechanical studies and general motion capture. One sensing device of the system is a linkage-based sensing structure comprising rigid links interconnected by revolute joints, where each joint angle is measured by a resistive bend sensor or other convenient goniometer. Such a linkage-based sensing structure is typically used for measuring joints of the body, such as the shoulders, hips, neck, back and forearm, which have more than a single rotary degree of freedom of movement. In one embodiment of the linkage-based sensing structure, a single long resistive bend sensor measures the angle of more that one revolute joint. The terminal ends of the linkage-based sensing structure are secured to the body such that movement of the joint is measured by the device. A second sensing device of the sensing system comprises a flat, flexible resistive bend sensor guided by a channel on an elastic garment. Such a flat sensing device is typically used to measure various other joints of the body which have primarily one degree of freedom of movement, such as the elbows, knees and ankles. Combining the two sensing devices as described, the sensing system has low sensor bulk at body extremities, yet accurately measures the multi-degree-of-freedom joints nearer the torso. Such a system can operate totally untethered, in real time, and without concern for electromagnetic interference or sensor occlusion.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. ProvisionalApplication Serial Nos. 60/044,495, filed Apr. 21, 1997, and 60/054,745,filed Aug. 4, 1997.

RELEVANT LITERATURE

[0002] U.S. Pat. No. 5,676,157, “Determination of KinematicallyConstrained Multi-Articulated Structures”, J. F. Kramer, describeskinematically constrained multi-articulated structures.

INTRODUCTION BACKGROUND

[0003] A growing market has developed for tools and systems that trackhumans and other bodies at rest and in motion. The applications for suchsystems vary considerably, and include such areas as the creation ofcomputer-generated and graphical animations, the analysis ofhuman-computer interaction, the assessment of performance athletics andother biomechanics activities, and the evaluation of workplace and otheractivities for general ergonomical fitness.

[0004] The possible sample uses for a body-tracking system are wide andvaried. For example, a user interested in creating a realistic computeranimation of a gymnast might be interested in tracking the full-bodymovements of the gymnast during a brief tumbling run characterized byhigh-velocity, high-acceleration activity. A second sample user mightinstead be interested in measuring the upper-body movements of a typicalclerical worker over a full workday, in order to assess the role ofvarious activities in causing repetitive stress injury. A third sampleuser might wish to record the motions of a high-performance skier orsnowboarder over a mile-long section of mountain in order to study andpossibly improve his or her technique.

[0005] The most general functional requirement of a body-tracking (ormotion-capture) device is that it accurately and reliably measure andreport the configuration of the various articulating members (limbs) ofthe body over a particular duration of interest. In order to be mostuseful, however, a motion-capture device must also satisfy additionalcriteria. It must be sufficiently lightweight and unencumbering to allowthe free performance of the activity being measured, (A system thatprevents an athlete or, performer from acting naturally, either due tothe addition of weight, to an impeding of balance and flexibility, or tothe presence of other physical constraints is clearly of lessenedutility as a motion-capture device). It must also allow for aperformance space appropriate to the motion being measured, i.e., itmust allow the user the freedom to move through space as needed tocomplete the activity being measured.

[0006] Various contributions to the prior art have addressed themselvesto the general problem of motion capture. Electromagnetic (E/M) trackingsystems, such as those manufactured by Polhemus and Ascension, usemultiple elements consisting of three orthogonally wound coils. At leastone such element is designated as a transmitter, and at least one suchelement is designated as a receiver. By energizing, in turn, the coilsin a transmitter element, and measuring the signal induced in thereceiver elements(s), the relative position of the transmitter andreceiver element(s) can be calculated. Such E/M tracking systems aresensitive to the presence of metal in the close surroundings and, inaddition, have a workspace limited by the requirement that thereceiver(s) remain within several feet of their correspondingtransmitter. Another disadvantage of E/M technology is that it typicallyincludes lag time which renders the position data non-real time.

[0007] As with E/M position sensing technology, ultrasonic (US) andinfrared (IR) position sensing technologies do not require a directtether between the hand and monitor. US and IR technologies have thedisadvantage, however, that they both require direct line of sight.Thus, when one hand passes in front of the other, the position signalcan be lost. Additionally, US technology, in particular, is verysensitive to ambient acoustic noise. Both technologies can introduce lagtime, again rendering the position data non-real time.

[0008] Another example of a prior art solution to the problem of motioncapture is a passive, optically-based body-tracking system, such as thatproduced by Motion Analysis. In such a system, multiple reflectivemarkers are attached to the surface of the limbs of interest, such thatthese markers are placed on either side of the articulating joints.Multiple cameras record the positions of these markers over time, andthis marker position data is used to extract (via “inverse kinematics”)the corresponding configurations of the various limbs and joints ofinterest. Such optical tracking systems have an inherent workspacelimitation that comes from the need to use cameras, namely that the userof the system is limited to the relatively small workspace that is bothvisible to the cameras and in focus. Tracking problems occur whenmarkers become occluded, since data cannot be recorded. In addition,such a system requires a non-trivial amount of post-processing of thedata; while it is expected that computing power and cost efficiency willcontinue to increase, optical systems still do not deliver on-the-spot,“real-time” data.

[0009] Still another example of a prior art solution is an active,optically-based body-tracking system. Such a system is conceptuallysimilar to the passive system described above, but with severaldifferences. The markers in such a system typically actively emit light,instead of being simple, passive reflectors. This allows the controllingsoftware to energize each of the markers in turn, and if properlysynchronized with the computer doing the data analysis, can help preventproblems that occur when the control software loses track of “whichmarker is which.” Otherwise, the workspace, marker-occlusion, andpost-processing shortcomings of such active optical systems are similarto that of the passive ones.

[0010] A Toronto-based company, Vivid Group, uses camera-basedtechnology called Mandela to monitor human motion without requiring theuser to wear any special devices. The system, however, only tracks bodymovements in two dimensions (2D). Most motion capture (MC) systemsrequire the user to wear some form of element that either is a sensoritself or is one component of a sensing system where other componentsare located off the user.

[0011] Still another example of a prior art solution is a theoreticalsimulation of the desired motion. By building a kinematic model of ahuman, attributing that model with realistic masses, rotational interiasand other properties, and specifying all relevant initial-condition andboundary constraints, it is theoretically possible to solve the dynamicequations of motion for a complex body. Once a solution has beengenerated, such information could be used to create graphical animationsor other imagery. There are several drawbacks, however. For example,such algorithmic solutions to motion capture are just now in theirinfancy and can be applied only in the most limited and constrained ofactivities. Also for example, the human brain is very good at detecting“incorrect” motion, so the performance demands on such a theoreticalsimulation will be very exacting. Also for example, such a system doesnot help at all with the problem of measuring the motion of livinghumans and is of little utility in biomechanics and ergonomicapplications.

[0012] There still remains a need for a position-sensing device which isaccurate, insensitive to environmental influences, has little lag timeand has high data rates.

SUMMARY OF THE INVENTION

[0013] A general overview of the inventive structure and method is nowprovided. The subject invention provides improvements, enhancements, andadditional patentable subject matter to the prior provisional patentapplication numbers U.S. Patent Application Serial Nos. 60/044,495,filed Apr. 21, 1997, and 60/054,745, filed Aug. 4, 1997, whichprovisional applications are incorporated herein in their entireties. Inparticular, the subject invention provides new shoulder- and hip-sensingstructures and techniques. In particular for each shoulder sensorassembly, this new structure and technique employs five long, thin,flexible strain-sensing goniometers to measure the overall angle of oneor more contiguous parallel-axis revolute joint sets. Theshoulder-sensing assembly is able to measure the angle of the humerusrelative to a fixed point on the back. A hip-sensing assembly similar inconstruction to the shoulder sensor is able to measure the angle of thefemur relative to a fixed point on the pelvis. Multiple parallel-axisjoints provide extensibility, such as a prismatic joint function, inaddition to providing the overall angle between the distal links of thetwo most extreme joints. In contrast, typical prismatic joints comprisedof one cylinder sliding inside another often exhibit sliding frictionand frequently bind if the forces between the cylinders are off axis. Bybuilding a “prismatic joint” from revolute joints, binding can beeliminated and resistance to movement greatly reduced.

[0014] As provided in this and the afore described provisional patentapplications, a very thin linkage with small diameter joints may befabricated, where flat, flexible bend sensors are used to measure thearc subtended by the distal links. To hold the bend sensors against thelinkage structure, special guides may be used. These guides provide achannel in which each sensor slides against its associated linkage as astructural joint is rotated. The guides also limit the range of motionof the neighboring joints. One or more guides may be fastened to a link.The guides for adjacent links are typically designed to come intocontact at a pre-determined joint angle, thus limiting joint range bypreventing the joint from bending further. The guides may be fastened tothe intended link in any convenient manner. In particular, the guidesmay have clips which allow them to snap around the intended link.

[0015] By way of overview, the Virtual Technologies' goniometer-basedbody-tracking device, equivalently referred to as the Range-Of-MotionSuit (ROMS) or the CyberSuit®, uses a bend-sensing technology to measurefive degrees of freedom of the leg and foot, and six degrees of freedomof the arm and wrist. The degrees of freedom (DOF) measured by oneembodiment of the present structure includes: ankle flexion, kneeflexion, hip abduction, hip flexion, hip rotation, wrist flexion, wristabduction, elbow flexion, shoulder flexion, shoulder abduction, andshoulder rotation. The present design directly extends to measurement offlexion, abduction and rotation of the lumbar and thoracic regions ofthe back, in addition to the neck. Means are also provided for measuringforearm rotation.

[0016] The CyberSuit measurement system includes a Lower ExtremityAssembly (LEA), an Upper Extremity Assembly (UEA), a Waist Pack Assembly(WPA), and VirtualBody® graphical body-simulation software. The LEA andUEA are Lycra®-based garments with pockets and fixtures for removablesensor assemblies. The WPA is a belt-mounted pack that contains all theinstrumentation electronics for data collection and logging. VirtualBodysoftware contains utilities for user calibration, graphical body model,and real-time data acquisition via the WPA A hand-held controller withLCD and six buttons serves as an optional user interface.

[0017] An overview of the CyberSuit is now described. The patentedVirtual Technologies, Inc. (Palo Alto, Calif.) resistive bend sensor(goniometer) (Kramer, et al, U.S. Pat. Nos. 5,047,952 and 5,280,265,which are hereby incorporated by reference) is the basis of theangle-sensing technology used in the CyberSuit. Sensors similar to thoseused in the Virtual Technologies CyberGlove product have beenincorporated into innovative multisensor assemblies to accommodate thelarger joints of the knee, ankle, elbow and wrist, and the complex balland socket joints of the shoulder and hip. Mechanically, the sensors arethin strips approximately 0.01″ thick, 0.20″ wide (minor axis), andvariable length (major axis). The sensor measures the angle between thetangents at its endpoints when the sensor assembly experiences purebending about the minor axis. The CyberSuit incorporates assemblieswhich use these sensors to accurately measure 1, 2 or 3 degrees offreedom, as appropriate, at each joint. Both the LEA and the UEAincorporate two types of sensor assemblies, a 1-DOF assembly used on theankle, knee, and elbow, and a 3-DOF assembly used on the hip andshoulder. The UEA also includes a 2-DOF sensor assembly, used on thewrist.

[0018] The CyberSuit incorporates the sensors in a Lycra suit with anembedded wiring harness, sensor pockets, connector pockets, and baseplates. The sensor pockets hold flat sensors used in 1-DOF and 2-DOFassemblies, which measure angles directly on the body. The base platesserve as fixation points for mechanical assemblies consisting ofmultiple, light, rigid links. The sensors are attached to the linkagesin such a way that they measure three degrees of freedom betweenrelevant major bones while bypassing intermediary body segments.

[0019] The inventive structure and method incorporate numerous designdetails and innovative elements, some of which are summarized below.Other inventive structures, methods, and elements are described in thedetailed description.

[0020] One innovative element, the 3-DOF assemblies, include theabove-mentioned mechanical linkages, with attached sensors, and the baseplate, fabric, and strap configuration which secures the linkage to thebody segments between which the relative orientation is being measured.The linkage assemblies typically consist of at least three segments,each of which contains many individual links but bends only in oneplane. This compound planar series of linkages measures the anglebetween linkage endpoints while permitting some translation of oneend-link with respect to the other. Using several of these linkagesegments achieves X-Y-Z translation and full range of motion for a bodyjoint. The linkage endpoints mirror the orientation of one bone withrespect to another so the sensors effectively measure the particularbone-to-bone angular orientation. The base plates are held to the suitin fabric pockets including straps which can be adjusted for each userin such a way as to maintain a known fixed orientation between thelinkage endpoint and the bones being measured. This linkage design andapplication allows for user-independent calibration of the linkageassemblies themselves. Due to the details of the linkage and jointgeometries, the design employs a method of attaching the sensors to thelinkages which captures and protects the sensor, maintains a fixedtangency with the linkage endpoints, and accommodates length changeswhich occur throughout the full joint range of motion. The use ofmulti-link planar segments allows significant translation withoutorientation change, which permits measurement over a full range ofmotion for a wide range of users. The link lengths are adjustable fordifferent users of more variant body types.

[0021] Another innovative element are the 2-DOF assemblies. The sensorconfiguration used on the wrist is designed to handle the special caseof a joint in which two degrees of freedom are measured and there is alimited range of motion. This design includes fan-shaped pockets andcorresponding tabbed bend sensor guides which physically decouple thetwo degrees of freedom being measured and allow each one to beaccurately measured with a single linear 1-DOF sensor.

[0022] The 1-DOF assemblies include 1-DOF joints which are directlymeasured with a sensor assembly encased in a flat fabric pocket sewn tothe Lycra material of the suit. The assembly consists of three layers:bottom and top guide layers of smooth plastic and a middle sensor layer.The guides are designed to protect and enclose the sensor while allowingfree sliding within the pocket and relative sliding between the sectionsto prevent buckling. The guide and pocket are also designed to maintainsensor endpoint tangency with the body part being measured. The designalso allows the sensors to be used by users with different limb lengthsand joint geometries and to accommodate these variations withoutadjustment. The sensor layer can consist of one long sensor or multiplesensors of various lengths which are electrically cascaded in series.These guides include devices to maintain endpoint tangency betweenconsecutive segments while allowing sliding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a diagrammatic illustration showing front (a) and rear(b) views of an exemplary embodiment of a 39-DOF Sensor Configuration.

[0024]FIG. 2 is a diagrammatic illustration showing front (a) and rear(b) views of an exemplary embodiment of a 22-DOF Sensor Configuration.

[0025]FIG. 3 is a diagrammatic illustration showing front (a) and rear(b) views of an exemplary embodiment of the 22-DOF Configurationillustrated in FIG. 2, including mounting details.

[0026]FIG. 4 is a diagrammatic illustration showing fundamental featuresof an exemplary resistive bend sensor, including (a) a mechanicalstructure and (b) the equivalent electrical circuit.

[0027]FIG. 5 is a diagrammatic functional block diagram showing themajor system functional blocks.

[0028]FIG. 6 is a diagrammatic illustration showing an overview ofexemplary signal amplification instrumentation contained in the DataAcquisition System.

[0029]FIG. 7 is a diagrammatic illustration showing (a) principles ofoperation of a bend sensor and (b) an exemplary single resistive bendsensor spanning two parallel-axis joints of a three-link mechanism.

[0030]FIG. 8 is a diagrammatic illustration showing an exemplary 1-DOFsensor assembly.

[0031]FIG. 9 is a diagrammatic illustration showing an exemplary 1-DOFassembly partially inserted into a fabric pocket on a suit.

[0032]FIG. 10 is a diagrammatic illustration showing an exemplaryapplication of a pair of 1DOF sensors configured to measure top and sidewrist angles.

[0033]FIG. 11 is a diagrammatic illustration showing an exemplarymechanical linkage element configuration for use on the right shoulderof the human body.

[0034]FIG. 12 is a diagrammatic illustration showing detail of theright-shoulder mechanical linkage in FIG. 11.

[0035]FIG. 13 is a diagrammatic illustration showing an exemplaryembodiment of a typical revolute joint between adjacent links.

[0036]FIG. 14 is a diagrammatic illustration showing an exemplaryembodiment of a typical revolute joint between adjacent links with theaddition of a typical set of guide stops around the links.

[0037]FIG. 15 is a diagrammatic illustration showing an explodedassembly of the structure in FIG. 14.

[0038]FIG. 16 is a diagrammatic illustration showing an exemplaryembodiment of a typical revolute joint with guide stops and a resistivebend sensor.

[0039]FIG. 17 is a diagrammatic illustration showing an explodedassembly of the structure in FIG. 16.

[0040]FIG. 18 is a diagrammatic illustration showing an exemplaryembodiment of a Guide Stop.

[0041]FIG. 19 is a diagrammatic illustration showing an exemplaryembodiment of an alternative linkage implementation, including both (a)assembled and (b) exploded views.

[0042]FIG. 20 is a diagrammatic illustration showing an exemplaryembodiment of a Mounting Plate for holding a mechanical linkage assemblyin functional relationship to the body of the wearer.

[0043]FIG. 21 is a diagrammatic illustration showing an explodedassembly of the structure in FIG. 20.

[0044]FIG. 22 is a diagrammatic illustration showing an embodiment of asimplified alternative mechanical linkage configuration for use on theright shoulder of the human body.

[0045]FIG. 23 is a diagrammatic illustration showing detail of a portion(link 0) of the right-shoulder mechanical linkage in FIG. 22.

[0046]FIG. 24 is a diagrammatic illustration showing detail of a portion(links 0 and 1) of the right-shoulder mechanical linkage in FIG. 22.

[0047]FIG. 25 is a diagrammatic illustration showing detail of a portion(links 1 and 2) of the right-shoulder mechanical linkage in FIG. 22.

[0048]FIG. 26 is a diagrammatic illustration showing detail of a portion(links 2 and 3) of the right-shoulder mechanical linkage in FIG. 22.

[0049]FIG. 27 is a diagrammatic illustration showing detail of a portion(links 3 and 4) of the right-shoulder mechanical linkage in FIG. 22.

[0050]FIG. 28 is a diagrammatic illustration showing detail of a portion(links 4 and 5) of the right-shoulder mechanical linkage in FIG. 22.

[0051]FIG. 29 is a diagrammatic illustration showing an exemplary SpinePlate.

[0052]FIG. 30 is a diagrammatic illustration showing (a) right sideview, (b) view perpendicular to plate, and (c) perspective view of anexemplary Spine Frames.

[0053]FIG. 31 is a diagrammatic illustration showing spine and armframes relative to a human body.

[0054]FIG. 32 is a diagrammatic illustration showing an exemplaryarrangement of linkages or joints for a right hip linkage assembly.

[0055]FIG. 33 is a diagrammatic illustration showing an exemplarysimplified alternative right hip linkage assembly.

[0056]FIG. 34 is a diagrammatic illustration showing an exemplary spineand leg frame mechanical assembly on a human body.

[0057]FIG. 35 is a diagrammatic illustration showing an exemplary hipplate frame mechanical assembly on a human body.

[0058]FIG. 36 is a diagrammatic illustration showing an exemplary wristand forearm assembly in a configuration appropriate for measuring thebending and rotation of the wrist and forearm.

[0059] FIGS. 37A-37I are diagrammatic illustrations showing a number ofdifferent embodiments of revolute joint sensors.

[0060]FIG. 38 is a diagrammatic illustration showing a flex sensor in a“living hinge” joint structure.

[0061]FIGS. 39A and 39B are diagrammatic illustrations showing a jointhousing a Hall-effect sensor.

[0062]FIGS. 40A and 40B are diagrammatic illustrations showing aHall-effect sensor in a “living hinge.”

[0063]FIG. 41 is a diagrammatic illustration showing the generaloperation of a Hall-effect sensor with associated magnet.

[0064]FIGS. 42A and 42B are diagrammatic illustrations showing theelectrical connections for a resistive bend sensor passing through aneighboring sensor of a joint.

[0065] FIGS. 43A-43D are diagrammatic illustrations showing commonfunctionality of four representations of two links adjoined by arevolute joint.

[0066] FIGS. 44 are diagrammatic illustrations showing the side views oftwo different joint-link structures and associated bend sensors.

[0067] FIGS. 45A-45D are diagrammatic illustrations showing thecomparison of a long bend sensor and a cascade of shorter sensors.

[0068]FIG. 46 is a diagrammatic illustration showing a shoulder sensorcomprising many revolute joints.

[0069]FIG. 47 is a diagrammatic illustration showing a canonicalarrangement of six revolute joints, shown here measuring the hip joint.

[0070]FIG. 48 is a diagrammatic illustration showing repeatedapplication of the canonical sensing assembly of FIG. 47.

[0071]FIG. 49 is a diagrammatic illustration showing a back-side view ofan embodiment of a body-sensing system.

[0072] FIGS. 50A-50D are diagrammatic illustrations showing a flexibledevice for measuring axial rotation.

[0073]FIG. 51 is a diagrammatic illustration showing the use of theflexible axial rotation sensor to measure the rotation of the forearmand leg.

[0074]FIG. 52 is a diagrammatic illustration showing another embodimentfor measuring forearm rotation.

[0075]FIG. 53 is a diagrammatic illustration showing the construction ofa resistive bend sensor comprising four resistive strain-sensingelement.

[0076]FIGS. 54A and 54B are diagrammatic illustrations showing two axialsensors.

[0077]FIG. 55 is a diagrammatic illustration showing a “ball joint”sensor.

[0078]FIG. 56 is a diagrammatic illustration showing a sensing systemwhich senses body functions and provides feedback.

[0079] FIGS. 57A-57C are diagrammatic illustrations showing the additionof bend sensors to the flexible axial rotation sensor.

[0080] FIGS. 58A-58C are diagrammatic illustrations showing variousspecialty joint-sensing devices.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0081] The inventive structure and method are now described in thecontext of specific exemplary embodiments. For convenience, but not byway of limitation, the description is partitioned into a systemoverview, a description of the kinematic foundation of the mechanicalcomponents and assemblies, and a description of elements, components,sensors, assemblies, and the like corresponding to the attached figures.

[0082] We now describe an overview of the inventive system andapparatus. In accordance with the subject invention, apparatuses areprovided which employ multiple links connected by revolute joints, formeasuring body parts, usually human body parts. The link and revolutejoint assembly has terminal links for fitting to mounts for the bodyparts. The mounts secure the terminal links to the body part to minimizemovement of the terminal links independent of the movement of the bodypart. Sensors are provided, where the sensor may extend past a pluralityof joints or the sensor may extend over a single joint, with theassembly comprising a plurality of the single sensor joints. Each ofthese structures has advantages for use in particular situationsdepending on the information to be processed from the apparatus.

[0083] A goniometer-based body-tracking system, referred to herein asthe Range-Of-Motion-Suit (ROMS), has been designed as a generalmeasurement tool for determining the positions of various joints on thehuman body. The principal components of the system are the LowerExtremity Assembly (LEA), the Upper Extremity Assembly (UEA) and theWaist Pack Assembly (WPA). The LEA, which measures lower-body joints,and the UEA, which measures upper-body joints, can be used eitherseparately or together. The WPA is a belt- or desk-mounted devicecontaining the Data Acquisition System (DAS) and various otherpower-supply and communications functions.

[0084] The LEA is a tights-like garment with protective fabric pocketshousing sensors to measure the ankle, knee and hip joints. It includes apair of socked feet to allow ankle instrumentation, mechanicalstiffeners to improve measurement accuracy and repeatability, and aseries of fabric channels to enclose sensor cabling, and connectorpockets to prevent snagging during use.

[0085] The UEA is an elastic garment extending from neck to mid-thigh,and covering the arms and hands. It includes fabric pockets housingsensors to measure the wrist, elbow and shoulder joints. Like the LEA,it also incorporates fabric channels to enclose sensor cabling, andconnector pockets to prevent snagging.

[0086] Resistive bend sensors, such as those described in U.S. Pat. Nos.5,047,952 and 5,280,265, (each of which is hereby incorporated byreference) form the basis of the angle-sensing technology used in thissystem. The bend sensors are thin, flexible strips that include twovariable-resistance elements. An encapsulant insulates and protects thesensing elements and the electrical connections from external damage.Four wires connect to solder tabs at one end of each sensor. A typicalsensor is shown in FIG. 4.

[0087] As a sensor element is bent about its minor axis, it undergoes achange in resistance. This change varies linearly with the change inangle between the ends of the sensor. The resistance is also moderatelydependent on any twist resulting from torsion about the sensor's majoraxis. For accurate measurement, therefore, it is important to allow onlypure bending of the sensor about its minor axis. The definition of theangle measured by the sensor and an equivalent electrical circuit forthe device are shown in FIG. 7 and FIG. 4 respectively.

[0088] The system must convert the small change in sensor resistanceproduced during bending into a usable signal. The instrumentationhardware that performs this function is the Data Acquisition System(DAS). The analog circuitry in the DAS conditions the sensor signals,multiplexes between sensor channels, performs fixed-gain amplificationof the sensor signal, applies channel-specific amplification offset andgain correction, and converts the resulting analog signal to a digitalvalue. Each of these operations is explained and discussed below. Thefunctional blocks in the overall DAS and the behavior of the analogsignal-conditioning circuitry are shown in FIG. 5 and FIG. 6,respectively.

[0089] The DAS measures changes in bend sensor resistance using aWheatstone bridge circuit. Each sensor provides two piezoresistiveelements for the bridge; the other half of the bridge consists of twohigh-precision reference resistors. The reference resistors are part ofevery sensor bridge, as an analog multiplexer is used to cycle throughall of the sensors in turn. The output of the Wheatstone bridge circuitis conditioned with a single-pole low-pass filter with a 3 dB frequencyof 100 Hz. The choice of cutoff frequency strikes a balance betweennoise rejection and frequency response requirements.

[0090] A 31-channel cascaded multiplexing system maps a particularsensor side of the bridge to one input of a fixed-gain instrumentationamplifier. The other differential input of the amplifier is alwaysconnected to the pair of precision reference resistors, which forms thereference side of the Wheatstone bridge. A fixed-gain amplificationstage, common for all sensor channels, converts the differential bridgesignal to a single-ended voltage. To map each individual sensor signaloptimally into the range of the analog-to-digital converter (ADC), eachsensor has an associated offset and gain value stored in EEPROM. As theDAS multiplexes through the sensor channels, it recalls thecorresponding gain and offset from EEPROM and uses them to setprogrammable components in the second amplification stage.

[0091] The sensor assemblies consist of two basic types: flat singledegree-of-freedom (1-DOF) assemblies that permit bending about one axisonly, and articulated mechanical (multi-DOF) assemblies that allow fullrotation between their endpoints. Both types of assemblies can becombined as needed to measure joints of interest on the human body. Thesensor assemblies are typically held in pockets sewn into the stretchfabric body of the LEA and UEA garments. The flat 1-DOF assembliestypically slide into long slender pockets and are held firmly againstthe body by the elasticity in the LEA or UEA garment. The multi-DOFassemblies are typically held in functional relation to the body by anarrangement of fabric pockets, mounting plates, straps and buckles.

[0092] We now discuss some of the kinematic foundations of themechanical assemblies. The underlying mathematical structure of thelinkage-based mechanical sensor assemblies is one involving kinematictransformation equations. These matrix equations describe the relativeposition and orientation of two rigid bodies with respect to oneanother. Applying several such transformations in succession allows forthe determination of the position and orientation of one end of anarticulating mechanical assembly with respect to the other. Thefollowing paragraphs give a very brief introduction to transformationkinematics in order to explain the function of the mechanical sensorassemblies, such as the right shoulder assembly that is used as thecanonical example. For a much more rigorous treatment of this material,see a standard robotics or dynamics text such as “Introduction toRobotics,” by John J. Craig, 1989.

[0093] Consider two R3 coordinate systems, characterized by two sets oforthonormal basis vectors designated as frame A and frame B. Theposition of a point P in space is independent of either of these twoframes, and can therefore be given equally well in terms of either ofthe two frame coordinate systems. The x, y, and z positions of point Pin frames A and B can be given by the following 4×1 matrices:$P_{A} = \begin{bmatrix}x_{A} \\y_{A} \\z_{A} \\1\end{bmatrix}$ $P_{B} = \begin{bmatrix}x_{B} \\y_{B} \\z_{B} \\1\end{bmatrix}$

[0094] A matrix equation is used to translate the coordinates of point Pin frame A to a different set of coordinates corresponding to theposition of point P in frame B. This equation is:$P_{A} = {\begin{bmatrix}R_{00} & R_{01} & R_{02} & x_{A\quad B} \\R_{10} & R_{11} & R_{12} & y_{A\quad B} \\R_{20} & R_{21} & R_{22} & z_{A\quad B} \\0 & 0 & 0 & 1\end{bmatrix}P_{B}}$

[0095] where R is a 3×3 direction cosines matrix expressing the relativeorientation of frame B with respect to frame A. (As a brief reminder,the three columns of R consist of the projections of the basis vectorsof frame B onto the basis vectors of frame A.) The first three elementsof the fourth column give the relative displacement of the two frames,i.e., this triad gives the coordinates for the origin of frame B interms of the basis vectors of frame A. If multiple successivetransformations are applied, then the matrices for each individualtransformation are multiplied together in order to determine the overalltransformation.

[0096] The resistive bend sensor used in the current implementation ofthis invention, as described in U.S. Pat. Nos. 5,047,952 and 5,280,265,(each of which are hereby incorporated by reference) measures the totalangle over which it spans, and therefore allows for the lumping togetherof multiple parallel-axis revolute joints into “joint sets” that can becharacterized with a single angle measurement. If this is done, however,it is no longer possible to determine the translation (fourth-column)vector between frames attached to two successive joint sets. Therefore,for simplicity, in all subsequent matrix derivations the translationvector in the fourth column of the generalized transformation matrix isreplaced with three zero values, and all subsequent discussion willconcentrate on the rotational component of the general transformationmatrix.

[0097] When all of the transformation matrices for moving from one frameto the next have been multiplied together, the resulting matrix givesthe net rotation from the first frame to the last. This information canbe used to translate the coordinates of a point from one frame to theother, but it can also be used to describe the relative orientation ofthe two frames without reference to a specific point. This is thetechnique used with the mechanical linkage sensor assemblies.

[0098] When using a multi-segment linkage assembly to measure therelative orientation of two body parts, such is as done at the hip andshoulder joints, there are generally four frames of interest:

[0099] Frame P, which fixed to the first (proximal) body part

[0100] Frame A, which is fixed to the proximal end of the linkageassembly

[0101] Frame Z, which is fixed to the distal end of the linkage assembly

[0102] Frame D, which is fixed to the second (distal) body part

[0103] The three basic components of any orientation measured by alinkage assembly are therefore:

[0104] T_(PA), which gives the orientation of the start of the linkagewith respect to the first body part

[0105] T_(AZ), which gives the orientation of the end of the linkagewith respect to the start of the linkage

[0106] T_(ZD), which gives the orientation of the second body part withrespect to the end of the linkage. For both the typical hip and shoulderexamples, the distal link is assumed to be always parallel to the distalbody part. This matrix, therefore, reduces to a simple one containingonly terms from the set {−1, 0, 1}.

[0107] Multiplying these three matrices together gives the netorientation of the second body part with respect to the first body part:

T _(PD) =T _(PA) T _(AZ) T _(ZD)

[0108] Once T_(PD) has been determined, it is a straightforward matterto express the relative orientation of the two body parts using any ofseveral desired representation schemes. Examples of methods fordescribing the relative orientation two coordinate frames include, butare not limited to:

[0109] Direction cosine matrices, which are 3×3 matrices that give thebasis vectors of the second frame in terms of those for the first frame

[0110] Fixed-frame (space) angle triads, where the second frame isinitially aligned with the first, then given three successive rotationsabout the first (stationary) frame axes.

[0111] Euler (body) angle triads, where the second frame is initiallyaligned with the first, then given three successive rotations about itsown (non-stationary) frame axes.

[0112] Angle-axis vectors, where the second frame is initially alignedwith the first, then given one rotation scalar about a single axisvector to bring it into its final position.

[0113] Quaternions, which use four parameters to express the rotation offrame 2 with respect to frame 1 in a mathematically useful way.

[0114] For this invention, the resulting T_(PD) is characterized usingEuler angle triads. This method happens to be convenient in thisapplication, as it tends to be more human-readable and intuitive thanthe other methods that require matrix or vector notation, but any of theabove may alternatively be used instead. When using the resultinginformation to build and render the image of a human body, for example,it may be more efficient to express the rotation using a directioncosines matrix, especially if the computer hardware being used has beenoptimized to perform very rapid matrix multiplication.

[0115] We now describe the inventive structure and method in the contextof particular exemplary structures, devices, elements, and assembliesillustrated relative to the figures.

[0116]FIG. 1 shows an exemplary arrangement for placing sensorassemblies on a human body. This configuration instruments most of themajor joints on the body, and (combined with devices to measure handmotion, e.g., a CyberGlove® instrumented glove made commerciallyavailable by Virtual Technologies, Inc., of Palo Alto, Calif., and a5^(th) Glove made commercially available by 5DT Corporation, SouthAfrica) affords body coverage that may, depending on the application, beconsidered as essentially complete. Sensors assemblies marked with a“(3)” after the name (not to be confused with a drawing referencenumeral) measure a full three rotational degrees of freedom. Sensorsmarked with a “(1)” or a “(2)” are located on joints with less thancomplete rotational freedom, and are therefore simpler devices.Assemblies include the upper back (3) assembly (101), Middle Back (3)assembly (102), Lower Back (3) assembly (103), Shoulders (3) assembly(104), Shoulder “Shrug” (2) assembly (106), Elbow (1) assembly (105),Forearm and Wrist (3) assembly (106), Hip (3) assembly (107), Knee (1)assembly (108), and Ankle (2) assembly (109). Each of these componentsor assemblies is disposed proximate or adjacent the associated humanbody part or parts as illustrated in the figure.

[0117] A particularly useful subset of the assemblies illustrated anddescribed relative to FIG. 1, is now described relative to FIG. 2. Theassemblies in FIG. 2 include: Shoulders (3) assembly (201), Elbow (1)assembly (202), Wrist (2) assembly (203), Hip (3) assembly (204), Knee(1) assembly (205), and Ankle (2) assembly (206). Again, each of theseassemblies are disposed proximate or adjacent to the associated humanbody part or parts as illustrated in the figure.

[0118]FIG. 3 shows further details for the sensor configuration given inFIG. 2. Each of the three degree-of-freedom linkage-based assemblies(300) is shown with corresponding endpoint plates (301), straps (303)and buckles (304). These hold the assembly in functional arrangement onthe body, and permit the mechanism to be firmly affixed to thecorresponding body parts. FIG. 3 also shows the belt-mounted WaistpackAssembly (WPA) (301), which includes the Data Acquisition System (DAS)and other system electronics. It can also be used in a desk-mounted modeor otherwise supported, using extension cables to transmit signalinformation from the sensors to the WPA.

[0119]FIG. 4a shows a mechanical overview of a resistive bend sensorpackage, including the minor axis (401) about which bending is intendedto occur. FIG. 4b shows an equivalent electrical circuit for the device,which consists of two resistive elements (405 and 406) arranged suchthan bending the sensor causes one resistance to increase and the otherto decrease.

[0120]FIG. 5 shows an overview (501) of the major functional blocks inthe main system. It consists of the sensors held in the LEA and UEAgarments (502), plus a Data Acquisition System (503) to process andtransmit sensor data to a host computer, including a processor (ormicroprocessor) input/ouptut port(s), memory, and other conventionalcomputer elements.

[0121]FIG. 6 shows an overview (601) of the signal amplificationinstrumentation contained in the DAS. Each pair of resistive sensingelements (602) is selected in turn by an analog multiplexer (606), thencompared with a pair of reference resistors (603) and excitation voltage(604) in a Wheatstone bridge configuration. Each sensor signal is sentthrough a first-order low-pass filter (605) with a corner frequency of100 Hz and is then preamplified (607). Each sensor signal is given achannel-specific gain and offset correction (608) to ensure that it isin the correct range for the subsequent analog-to-digital converter(609).

[0122]FIG. 7a shows the fundamental operating principles of theresistive bend sensor (701) of U.S. Pat. Nos. 5,047,952 and 5,280,265.This sensor produces a signal whose output change is proportional to thechange in angle (703) between its ends. This behavior makes it ideal formeasuring the sum of the angles about multiple parallel axes. FIG. 7bshows a single resistive bend sensor spanning two parallel-axis joints(705) of a three-link (704) mechanism. As this figure shows, the angle(706) reported by the resistive bend sensor is equal to the sum of theindividual angles spanned by this instrument. This principle can be alsobe used to measure the combined angle across three or more parallel-axisjoints.

[0123]FIG. 8 shows a sensor assembly (801) that uses the resistive bendsensor (804) to measure a single rotational degree of freedom. In thisimplementation, the sensor is constrained by two long flat plasticguides (802 and 803), as well as a number of guiding spacers (805). Thisarrangement ensures that the sensor bends about its short axis only, sothat it neither twists nor yaws. Such assemblies are flat andlow-profile, and are appropriate for measuring body joints with only oneclear axis of rotation. Examples of such joints include the knee and theelbow.

[0124]FIG. 9 shows the partial insertion of a typical 1DOF sensorassembly (901) into a fabric pocket (902) on the suit. Other methods ofattachment of the sensor may alternatively be employed.

[0125]FIG. 10 shows an useful application of a pair of typical 1DOFsensors (1001 and 1002) configured to measure the top and side wristangles of the hand. Each sensor is held in a fan-shaped fabric pocket(1003 and 1004), which allows the sensors to slide laterally whenbending occurs around the axis of the other sensor. This effectivelydecouples the two motions, and allows the joint to be treated as a pairof independent single-DOF revolute joints, instead of as a compound,two-DOF joint.

[0126]FIG. 11 shows a sample configuration of mechanical linkageelements (1101), arranged in a fashion appropriate for use on the rightshoulder of the human body. At both the proximal (spine) and distal(arm) ends of the mechanical structure, the linkage is held to the bodywith a fastening arrangement (1102 and 1103). These fasteningarrangements ensure that the structure is held firmly to the body andtherefore tracks closely any motion made by the wearer. In practice, asensor such as a resistive bend'sensor is associated with each joint.Alternate goniometers may conveniently be employed, such as Hall-effectsensors, optical encoders, potentiometers, resolvers and the like.

[0127]FIG. 12 shows a close-up of the sample right-shoulder linkageshown in FIG. 11. The line at each of the revolute joints represents theaxis of rotation for that joint. As discussed, resistive bend sensorscan span more than one revolute joint, so parallel joints can begathered conceptually into “joint sets.” These joint sets (1201, 1202,1203, 1204 and 1205) may be measured with a single such bend sensor. Asshown, this particular shoulder configuration includes five joint setsand therefore requires five bend sensors to instrument fully. As thenumber of joint sets is increased beyond the theoretical minimumrequired to allow full range of motion, the linkage can be made to lieflatter to the body and be correspondingly less intrusive to the wearer.The sample configuration shown is a typical one, and achieves areasonable balance between the two goals of minimizing theinstrumentation complexity and minimizing the profile of the device.

[0128]FIG. 13 shows a typical revolute joint between two adjacent links(1301 and 1302) in a mechanical assembly such as the one shown in FIG.12. This joint shown here can take any number of forms, including (butnot limited to) a pinned joint, a tongue-and-groove joint, a jointbetween molded plastic parts with integral detente features, a jointbetween self-lubricating materials, a joint incorporating a bushing, ora joint incorporating a bearing. In general, the particular jointimplementation will involve a trade-off between performance and someother factor, such as cost, weight or complexity of assembly. A typicalimplementation for such a joint uses a dowel pin (1303) to join twoself-lubricating plastic parts.

[0129]FIG. 14 shows a typical link pair (1401 and 1402), but with theaddition of a typical set of guide stops (1404, 1405, 1406 and 1407)around the links. These guide stops are useful for limiting the anglethrough which any particular joint can revolve. They are also useful forcovering and protecting any bend sensor lying along the linkageassembly. In the sample configuration shown, the guide stops consist ofpairs of plastic covers, enclosing the linkage in a clamshell fashion.The sample shown includes integral angle constraints, as well as achannel between the link and the guide to allow passage of a bendsensor.

[0130]FIG. 15 shows the same sample link pair (1501 and 1502)configuration given in FIG. 14, but with the various constituent partsexploded to show assembly. In this sample configuration, a dowel pin(1503) joins the two plastic links, and the pairs of guide stops (1504,1505, 1506 and 1507) are attached in a clamshell fashion around theircorresponding links.

[0131]FIG. 16 shows a typical link pair (1601 and 1602) with guide stops(1604, 1605, 1606 and 1607), but with the addition of a resistive bendsensor (1608) on the top surface of the link pair. As shown, the sensoris protected by the set of guide stops and is further constrained tobend about its short axis only.

[0132]FIG. 17 shows the same sample link pair (1701 and 1702)configuration given in FIG. 16, but with the various constituent partsexploded to show assembly and the position of the bend sensor (1708).

[0133]FIG. 18 shows a close-up view of a typical guide stop (1801) fromthe configuration given in FIGS. 14 through 17. In this configuration,angle constraints are applied to the joint motion by the interferencebetween the faces (1802) of adjacent guide stops. A gap (1803) forallowing passage of a bend sensor is included, as is a region (1804) toprevent the bend sensor from being pinched during joint motion.

[0134]FIG. 19a shows an exploded assembly view of three links inanother, alternate arrangement for an articulating mechanical sensorassembly. In this version, the bend sensor (1901) lies on the neutralaxis of the linkage (1902) cross-section, instead of in an off-axisposition as in the design shown in FIG. 17. (This feature has theadvantage of causing little motion in the free end of a bend sensor asthe mechanism articulates, which simplifies linkage selection andmechanism synthesis.) A bend sensor is shown in the middle, encased inself-lubricating plastic link halves. The link elements shown are joinedusing self-tapping screws (1903) to facilitate assembly and disassembly,although they may also be joined using integrally molded snap-fitelements. Holes are included in the sides of the links to provide accessto sensor wiring. FIG. 19a shows this design with the links in theirtypical assembled state (1904).

[0135]FIG. 20 shows a typical arrangement for holding a mechanicallinkage assembly in functional relationship to the body of the wearer.The square cross-sectioned hole (2006) made by the endpoint holder(2003) and the spacer (2002) acts as a receptacle for the final link ofthe linkage structure, which is held secure by a screw threaded (2004)into the endpoint holder. The curved plate (2001) fits flush to thebody, and is adjusted to be held firmly by nylon straps passed throughslots (2005) in the plate. The arrangement detailed in this figure isthe one typically used to hold the shoulder and hip assemblies to thearms and legs, respectively.

[0136]FIG. 21 shows an exploded view of FIG. 20. In this implementation,the parts are joined with adhesives and dowel pins (2103), although thenecessary fixation can be achieved with a wide variety of structures andmethods. For example, the linkage can be attached to the fixation platevia methods that include (but are not limited to) a threaded fastener, adétented snapfit between link and holder, a cam lock, a friction fit, orthe like.

[0137]FIG. 22 shows a simplified version of the typical right shoulderlinkage given in FIG. 12. As discussed, a resistive bend sensor can bespanned over multiple parallel-axis revolute joints in order to measurethe sum of the angles across these joints. This feature allows for areduction in the number of sensors without any corresponding loss ofrotation information, since each of the “joint sets” shown in FIG. 12can be instrumented with a single sensor. FIG. 22 replaces each of thejoint sets in FIG. 12 with a single joint connecting simplified links(2200, 2201, 2202, 2203, 2204 and 2205) in order to simplify thederivation of the kinematic transformation equation across the completeright-shoulder assembly.

[0138] Note that this technique results in a loss of translationalinformation, as it becomes no longer possible to determine thedisplacement vector between the proximal and distal ends of the linkageonce the individual joints comprising a joint set have been lumpedtogether in this fashion. For body-measurement applications, however,this is not a concern, as kinematic constraints provided by human-bodygeometry allow for the determination of the body position. For example,the joint motions that comprise a human shoulder can, to a reasonabledegree of accuracy, be modeled as a ball-and-socket joint with a fixedcenter of rotation. This assumption, combined with a knowledge of therelative orientation between the upper torso and the humerus bone,suffices to fix both the position and orientation of the upper arm. Ifit ever becomes necessary to explicitly measure the actual displacementvector between the ends of the mechanical linkage in addition to therotation information, then this can be accomplished by either (1)limiting the choice of joint sets to the trivial case where each setcomprises a single revolute joint only, or (2) using a single resistivebend sensor for each revolute joint. Note that if practical, option (2)is preferred since the redundant joints are added to allow fortranslation between various joint set, and also to provide betterconformity of the mechanical structure to the contour of the body.

[0139] FIGS. 23 to 28 show close-up views of portions of the rightshoulder mechanism given in FIG. 22. They define exactly the variousangles that comprise a typical right shoulder assembly. Note that inorder to make the assembly best fit the body, the first angle is a fixedoffset, followed by five revolute joint angles which are variable andare typically measured using resistive bend sensors. Recall, however,that any convenient goniometer as listed previously may be substituted.The frame and angle derivations for this mechanism are representative ofthose used in a generalized mechanical linkage assembly and aretherefore given in full detail.

[0140] With any mechanical sensor assembly described here, frame A isdefined as the frame attached to the first (proximal) link, and frame Zis that attached to the final (distal) link. To facilitate thederivation of the T_(AZ) matrix for this mechanism, the intermediateframes a through g have been used. Frame a is identical to frame A, andframe g is identical to frame Z.

[0141] We now summarize the structures illustrated in FIGS. 23 through28. FIG. 23 shows a close-up of link 0 (2300), and is used to defineT_(ab) (2305) using the fixed offset angle, q₀ (2304). FIG. 24 shows aclose-up of links 0 (2400) and 1 (2401), and is used to define T_(bc)(2405) using the bend sensor angle q₁ (2404). FIG. 25 shows a close-upof links 1 (2501) and 2 (2502), and is used to define T_(cd) (2506)using the bend sensor angle q₂ (2505). FIG. 27 shows a close-up of links3 (2701) and 4 (2702), and is used to define T_(ef) (2706) using thebend sensor angle q₄ (2705). Finally, FIG. 28 shows a close-up of links4 (2801) and 5 (2802), and is used to define T_(fg) (2806) using thebend sensor angle q₅ (2805).

[0142] The corresponding coordinate transformations are as follows:$\begin{matrix}{\left( T_{a\quad b} \right)_{R\quad S\quad H} = \begin{bmatrix}{\cos \quad \theta_{0}} & {{- \sin}\quad \theta_{0}} & 0 & 0 \\0 & 0 & {- 1} & 0 \\{\sin \quad \theta_{0}} & {\cos \quad \theta_{0}} & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}} & {\left( T_{d\quad e} \right)_{R\quad S\quad H} = \begin{bmatrix}{\cos \quad \theta_{3}} & {{- \sin}\quad \theta_{3}} & 0 & 0 \\0 & 0 & {- 1} & 0 \\{\sin \quad \theta_{3}} & {\cos \quad \theta_{3}} & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}} \\{\left( T_{b\quad c} \right)_{R\quad S\quad H} = \begin{bmatrix}{\cos \quad \theta_{1}} & {{- \sin}\quad \theta_{1}} & 0 & 0 \\0 & 0 & {- 1} & 0 \\{\sin \quad \theta_{1}} & {\cos \quad \theta_{1}} & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}} & {\left( T_{e\quad f} \right)_{R\quad S\quad H} = \begin{bmatrix}{\cos \quad \theta_{4}} & {{- \sin}\quad \theta_{4}} & 0 & 0 \\0 & 0 & 1 & 0 \\{{- \sin}\quad \theta_{4}} & {{- \cos}\quad \theta_{4}} & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}} \\{\left( T_{c\quad d} \right)_{R\quad S\quad H} = \begin{bmatrix}{\cos \quad \theta_{2}} & {{- \sin}\quad \theta_{2}} & 0 & 0 \\0 & 0 & 1 & 0 \\{{- \sin}\quad \theta_{2}} & {{- \cos}\quad \theta_{2}} & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}} & {\left( T_{f\quad g} \right)_{R\quad S\quad H} = \begin{bmatrix}{\cos \quad \theta_{5}} & {{- \sin}\quad \theta_{5}} & 0 & 0 \\0 & 0 & {- 1} & 0 \\{\sin \quad \theta_{5}} & {\cos \quad \theta_{5}} & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}}\end{matrix}$

[0143] Once the various constituent transformation matrices have beendefined and calculated, the resultant transformation across the rightshoulder sensor assembly can be determined according to the equation:

(T _(AZ))_(RSH)=(T _(ab))_(RSH)(T _(bc))_(RSH)(T _(cd))_(RSH)(T_(de))_(RSH)(T _(ef))_(RSH)(T _(fe))_(RSH)

[0144] In FIG. 29, there is shown a close-up view of a typical spineplate (2901) that includes holders (2902) used to fix the first(proximal) ends of the typical right (2904) and left (2903) shoulderlinkages to the body. It fits in a fabric pocket on the suit and can beheld securely in place with appropriate fasteners.

[0145] In FIG. 30, there are shown three views of the spine plate (3003)illustrated in FIG. 29. These views are used to define the T_(PA) matrix(3004) that expresses the relative orientation of frame A (3002), theframe attached to the first (proximal) right shoulder link with respectto frame P (3001), the frame attached to the spine, which is in thisexample taken to be the proximal body part for a shoulder-anglemeasurement. The relative orientation of the two frames is described bytwo angles, α_(RSH) (3003) and β_(RSH) (3004). As shown in the figure,β_(RSH) is the angle in a right side view between the spine and theplate, and α_(RSH) is the angle of the first shoulder link with respectto the spine plate's vertical centerline.

[0146]FIG. 31 shows the spine plate (3101) and final (distal) rightshoulder linkage (3105) on the body. For any particular body part andmechanical assembly, a “zero position” must be defined. For the typicalright shoulder assembly, this has been defined as the configuration withthe arm at the side and the palm facing inward. (Note that thisconfiguration is not the same as the so called “anatomical position”,which has the palm facing forward.)

[0147] In the zero position, the frame P attached to the proximal bodypart (3106) and the frame D attached to the distal body part (3107) are,by definition, exactly aligned. When the frames are aligned, a (0,0,0)Euler angle triad is used to describe the orientation between the twobody part frames, so the term “zero position” is a natural one.

[0148] Once frames P and D have been aligned in this way, the definitionof T_(ZD) follows. To simplify system calibration, it is assumed thatthe distal link and distal body part are aligned with each other. Thematrix T_(AD) is therefore a simple one. For example, for the typicalright shoulder assembly the matrix T_(ZD) given by the expression:$\left( T_{Z\quad D} \right)_{R\quad S\quad H} = \begin{bmatrix}0 & 0 & 1 & 0 \\{- 1} & 0 & 0 & 0 \\0 & {- 1} & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}$

[0149]FIG. 32 shows the arrangement of the linkages for a typical righthip linkage assembly. As in FIG. 12, which shows the five “joint sets”for the right shoulder assembly, the joints for this typical hip linkagecan be collected into three joint sets (3201, 3202 and 3203). Alldiscussions of joint sets for the right shoulder mechanism apply equallyto that for the right hip.

[0150]FIG. 33 shows the four-link (3307, 3308, 3309 and 3310) kinematicequivalent of the right hip assembly, which is obtained by replacingeach hip joint set by a single revolute joint. The frame attached to thefirst link, frame A (3301), is shown, as is the frame attached to thelast link, frame Z (3302). The axes and directions of the three hip bendsensor angles (3303, 3304 and 3305) are also shown; these angles are allzero when the hip assembly is fully straight. The resulting matrix(3306) expressing the relative orientation of the last hip link withrespect to the first hip link is:$\left( T_{A\quad Z} \right)_{R\quad H\quad I\quad P} = \begin{bmatrix}{{\cos \quad \theta_{1}\cos \quad \theta_{2}\cos \quad \theta_{3}} - {\sin \quad \theta_{1}\sin \quad \theta_{3}}} & {{\cos \quad \theta_{1}\cos \quad \theta_{2}\cos \quad \theta_{3}} - {\sin \quad \theta_{1}\sin \quad \theta_{3}}} & {\cos \quad \theta_{1}\sin \quad \theta_{2}} & 0 \\{{\sin \quad \theta_{1}\cos \quad \theta_{2}\cos \quad \theta_{3}} + {\cos \quad \theta_{1}\sin \quad \theta_{3}}} & {{{- \sin}\quad \theta_{1}\cos \quad \theta_{2}\sin \quad \theta_{3}} + {\cos \quad \theta_{1}\cos \quad \theta_{3}}} & {\sin \quad \theta_{1}\sin \quad \theta_{2}} & 0 \\{{- \sin}\quad \theta_{2}\cos \quad \theta_{3}} & {\sin \quad \theta_{2}\sin \quad \theta_{3}} & {\cos \quad \theta_{2}} & 0 \\0 & 0 & 0 & 1\end{bmatrix}$

[0151]FIG. 34 shows the typical right hip mechanical assembly on thebody. The linkage endpoint fixation method is not shown, but isfunctionally equivalent to that used for the typical right shoulder, asshown in FIGS. 20 and 21. As with the right shoulder, a “zero position”must be selected at which the frames attached to the proximal (3403) anddistal (3406) body parts are defined to be exactly aligned. For thetypical right hip, this was chosen as the natural standing position withthe foot facing forward. As with the right shoulder, the distal hip linkand the second body part (the femur) are assumed to be aligned. Fromthis choice of zero position aligning frames P and D, transformationT_(ZD) (3407) must be:$\left( T_{Z\quad D} \right)_{R\quad H\quad I\quad P} = \begin{bmatrix}0 & {- 1} & 0 & 0 \\0 & 0 & 1 & 0 \\{- 1} & 0 & 0 & 0 \\0 & 0 & 0 & 1\end{bmatrix}$

[0152]FIG. 35 shows hip plate frames including a close-up of the top ofthe typical right hip assembly, and includes the frames and anglesneeded to define T_(PA) (3507) for this mechanism. Unlike T_(PA) for thetypical right shoulder, which is described by two Euler-angleparameters, the matrix for the right hip assembly requires three:α_(RHIP), β_(RHIP), and γ_(RHIP) (3504, 3505 and 3506). Recall thatframe P (3502) is defined as the frame attached to the proximal bodypart, and frame A (3503) is defined as the frame attached to the first(proximal) link in the hip assembly. Before these three angles areapplied to frame A, it is initially aligned with frame P. From thisstarting orientation, Frame A is first rotated about the spine axis bythe angle π+α_(RHIP), then about its outward normal by the angleβ_(RHIP), then about its upper outside edge by the angle γ_(RHIP.) FIG.35 shows the final orientation of frame A, along with the exactdefinitions of the three rotations described above. Based on theserotations, the resulting T_(PA) is:$\left( T_{P\quad A} \right)_{R\quad H\quad I\quad P} = \begin{bmatrix}{{\sin \quad \alpha_{RHIP}\sin \quad \beta_{RHIP}\sin \quad \gamma_{RHIP}} - {\cos \quad \alpha_{RHIP}\cos \quad \gamma_{RHIP}}} & {\sin \quad \alpha_{RHIP}\cos \quad \beta_{RHIP}} & {{{- \sin}\quad \alpha_{RHIP}\sin \quad \beta_{RHIP}\cos \quad \gamma_{RHIP}} - {\cos \quad \alpha_{RHIP}\sin \quad \gamma_{RHIP}}} & 0 \\{\cos \quad \beta_{RHIP}\sin \quad \gamma_{RHIP}} & {{- \sin}\quad \beta_{RHIP}} & {{- \cos}\quad \beta_{RHIP}\cos \quad \gamma_{RHIP}} & 0 \\{{{- \cos}\quad \alpha_{RHIP}\sin \quad \beta_{RHIP}\sin \quad \gamma_{RHIP}} - {\sin \quad \alpha_{RHIP}\cos \quad \gamma_{RHIP}}} & {{- \cos}\quad \alpha_{RHIP}\cos \quad \beta_{RHIP}} & {{\cos \quad \alpha_{RHIP}\sin \quad \beta_{RHIP}\cos \quad \gamma_{RHIP}} - {\sin \quad \alpha_{RHIP}\sin \quad \gamma_{RHIP}}} & 0 \\0 & 0 & 0 & 1\end{bmatrix}$

[0153]FIG. 36 shows a typical arrangement of linkage elements into amechanical sensing assembly, in a configuration appropriate formeasuring the bending and rotation of the wrist and forearm. Based onthe “joint set” notation introduced in the right shoulder and right hipassemblies, this configuration is characterized as having five jointssets (3603, 3604, 3605, 3606 and 3607) and would require five resistivebend sensors. The proximal end of the assembly is fixed to a fasteningdevice (3601) located just below the elbow, and the distal end of theassembly is fixed to a fastening device (3602) located on the hand.

[0154] In FIGS. 37 to 40 are depicted a number of different embodimentsof hinge sensors, which find applicability for use in the revolutejoints of the linkage-based sensing devices. The hinge sensors of FIGS.37 to 40 may be substituted at the various joints, as appropriate for aspecific design.

[0155] In FIG. 37 a number of related, but different embodiments ofhinge sensors are depicted. In the different embodiments, the sensor iscapable of passing through the axis of the joint or generally bows awayfrom the axis of the joint. In FIG. 37A, the sensor is shown passingthrough the axis of the joint. The hinge 3700 has an external yoke 3701and an internal yoke 3702 in mating relationship to form an “open”hinge. Pins 3703 and 3704 connect yokes 3701 and 3702 and define therotational axis of the hinge 3700. The sensor 3705 is rigidly affixed atits ends to the inner surfaces 3706 and 3707 of yokes 3701 and 3702,respectively. Links 3708 and 3709, shown fragmented, extend from yokes3701 and 3702, respectively. While the embodiment is depicted with thesensor rigidly affixed to the internal surfaces of the yokes, one orboth of the sensor ends can be guided to move relative to the yoke.

[0156] In FIG. 37B is shown a side cross-sectional view of FIG. 37A,showing the hinge 3700 with the sensor 3705 passing through the hingeaxis and having its ends affixed to the yokes. In FIG. 37C is shown aside cross-sectional view, where a hinge 3710 comparable to the hinge ofFIG. 37A is shown, with sensor 3711 having each of its ends in channels3712 and 3713, respectively. Channels 3712 and 3713 extend into links3714 and 3715, respectively. With movable ends, the sensor is able toposition itself to assume a curve of low resistive force.

[0157] In FIG. 37D is depicted a “closed” hinge 3720, formed by externalyoke 3721, attached to link 3725, in conjunction with link 3722. Link3722 has protuberances 3723 on opposite sides of the link 3722, whichprotuberances extend into concavities in yoke 3721, thereby forming ahinge. The sensor 3724 is affixed at end 3726 to yoke 3721 and at end3727 to link 3722. An alternate hinge structure is shown in FIG. 37E,where the ends of the links 3730 and 3731 have mating L-shaped ends 3732and 3733, respectively. Pin 3734 extends through the L-shaped ends 3732and 3733 to define the hinge. The sensor 3735 is placed over the links3730 and 3731 extending over the pin 3734, with the sensor ends affixedto the links 3730 and 3731, by means such as clips, glue or otherconvenient fastening means. While the embodiments in FIGS. 37D and 37Eare depicted with the sensor rigidly affixed to the internal surfaces ofthe yokes, one or both of the sensor ends can be guided to move relativeto the yoke.

[0158] In FIG. 37F an exemplary cross-section of both FIGS. 37D and 37Eis shown, wherein the sensor 3740 is shown affixed at its ends to links3741 and 3742, to bow around the axis 3743. Links 3741 and 3742 areshown aligned. In FIG. 37G, the links 3741 and 3742 are shown unaligned,with sensor 3740 bowing a greater distance away from axis 3743. FIGS.37H and 37I provide exemplary cross-sections of both FIGS. 37D and 37E,wherein the sensor 3744 has at least one of its ends 3745 able to slidein a channel 3746. Channel 3756 extend into link 3747. With at least onemovable end, the sensor is able to position itself to assume a curve oflow resistive force.

[0159]FIG. 38 provides a flex-sensing goniometer 3801 (such as thevariable strain-sensing goniometers disclosed in U.S. Pat. Nos.5,047,952 and 5,280,265 by Kramer, et al.) housed in a flexible “living”hinge structure 3800. Other flex-sensing goniometer technologies anddesigns, such as a fiber-optic flex sensor, may also be housed in theliving hinge structure. FIG. 38A provides a cross-sectional view whileFIG. 38B provides a perspective view. The electrical connections 3802and 3803 for the goniometer are incorporated in links 3804 and 3805. Inthis embodiment, 3802 is the electrical connection to goniometer 3801,while 3803 is an electrical connection which passes electricallyunaltered through goniometer 3801 and provides the connection for asecond goniometer (not shown) at another portion of link 3805. Suchelectrical connections may take the form of wires, metal traces,conductive polymers, conductive inks, or other such electricallyconductive paths. Constructed as such, all goniometers and electricalconnections can be housed inside the link-joint structure. Thegoniometer with its electrical connections can be placed inside thelink-joint structure in a variety of ways, including being molded intothe structure. Printed circuit techniques, including etching,deposition, and other techniques, which are well known in theelectronics industry, may be employed to fabricate such goniometers andtheir associated electrical connections.

[0160] The flex-sensing goniometer may be positioned inside the flexiblehinge. Typical hinge materials are plastics and metals which can endurea large number of bend cycles without becoming mechanically damaged. Asshown in the cross-section view of FIG. 38A, preferably the goniometeris positioned such that its neutral bend axis is aligned with theneutral bend axis of the flex hinge. The goniometer can lie totallywithin the hinge material or be only partially covered. The goniometeritself can also be the flex hinge, providing both the angle measurementas well as the material structure of the hinge.

[0161] In one embodiment, as shown in FIGS. 39A and 39B, a joint 3900houses a Hall effect goniometer comprising a Hall effect sensor 3901 andmagnet 3902, which goniometer is employed at the joint to measure theangle between links 3904 and 3906. Other orientations of the sensor andmagnet may be employed to improve the structural profile of the sensor,although the depicted embodiment maximizes the range of the sensor. Thetwo mating parts 3903 and 3905 of the joint are substanitally mirrorimages, each one having a pin, 3907 and 3908, which sits in a groove,3909 and 510, respectively, defining an axis of joint rotation. The Halleffect sensor 3901 is located in the part of the joint 3903 at the endof link 3904, while the magnet 3902 is located in the part 3905 at theend of link 3906. Such Hall effect goniometers may be employed formeasuring the angles at any joint between associated links.

[0162] Alternatively, as shown in FIGS. 40A and 40B, a joint 4000 with aflexible hinge 4001 is used, which can be molded to the appropriategeometry. A Hall effect goniometer comprising sensor 4002 and magnet4003 is employed to measure the angle of the joint 4000. The Hall effectgoniometer components 4002 and 4003 are positioned to move relative toeach other due to the flexibility of regions 4004 and 4005. Sensor 4002follows the movement of link 4006 in fixed alignment. Similarly, magnet4003 follows the movement of link 4007 in fixed alignment. Channel 4008separates sensor 4002 from magnet 4003 and defines the hinge region. Theflexible hinge regions 4004 and 4005 are “living hinges,” which define abend axis as the regions flex. The bend axis is the axis about which thetwo links articulate. In FIG. 40B is shown a perspective view of joint4000. The appearance of the joint 4000 is exemplary of one form andlarge variations may be made while retaining the function of the joint.Inside the box housing 4010 is sensor 4002 (shown with broken lines)shown as a rectangularly shaped sensor, while in housing 4011 is themagnet (shown with broken lines) shown as a cylindrically shaped magnet.

[0163]FIG. 41 presents the general operation of a Hall goniometer. InFIGS. 41A and 7B are depicted the extreme positions of the Hall sensor4100. In FIG. 41A, sensor 4100 in an aligned configuration with themagnetic field 4102 of magnet 4101, producing minimum signal. In FIG.41B, sensor 4100 is orthogonal to the magnetic field 4102, whichprovides the maximum signal. The different positions between the extremepositions measure the various angles defined by the links attached tothe joint comprising the Hall sensor and magnet.

[0164] The various hinges depicted in FIGS. 37 and 39 provide that whenboth ends of the sensors are fixed to the links, it is possible to havethe electrodes for the sensors take the form of electrical tracespassing through the links. The traces for a distal joint sensor can alsopass through the sensor of a joint proximal to one end of the device.This is depicted in FIGS. 42A and 42B. FIG. 42A has flex sensors 4201and 4202 straddling joints 4203 and 4204, respectively. The electricalconnections for sensor 4201 with sensing grid 4213 are incorporated intolink 4205 as traces 4208, the associated non-sensing flex circuit traces4209 pass through the neutral axis of sensor 4202, continue into link4206 as traces 4210 and terminate at electrodes 4207 on sensor 4201.Trace 4211 is shown to terminate at electrodes 4212 on sensor 4202 whichhas sensing grid 4214. Although not shown, traces 4208 and 4211 lead toinstrumentation circuitry. FIG. 42B shows a plan view of the devicedepicted in FIG. 42A with the elements corresponding thereto.

[0165] FIGS. 43A-43D provide the common functionality of fourrepresentations of two links adjoined by a revolute joint. In FIG. 43A,link-joint-link device 4300 comprises two links 4302 and 4303,represented by single line segments, connected by revolute joint 4301,represented by a cylinder. The axis of rotation of such a diagrammaticaljoint is parallel to the long axis of the cylinder. In FIG. 43B,link-joint-link device 4304, the joint is represented by two cylinders4305 and 4306 which rotate relative to each other along an axis ofrotation which is again parallel to the long axis of each cylinder.Joint 4308, represented by a line segment, is connected to joint portion4305, while link 4307 is attached to joint portion 4306. In FIG. 43C, alink-joint-link device 4309 is shown, which is similar to the jointstructure provided in FIG. 13. Here links 4311 and 4310 rotate relativeto each other about the joint axis defined by pin 4312. Theimplementational details of the hinge are provided by the tongue 4313and groove 4314 structure. In FIG. 43D, link-joint-link device 4315comprises links 4316 and 4317 which rotate relative to each other aboutjoint axis 4318. In FIG. 43D, the axis is diagrammatically depicted onlyas a solid line, where the axis of rotation is coincident with the line.Any of the various joint representations may be used to explain thekinematic articulations of a structure, when the specific details of thejoint construction is not critical for the explanation.

[0166]FIGS. 44A and 44B provides the side view of two differentlink-joint-link structures where a single sensor may be used to providethe overall joint angle. The structure 4400 in FIG. 44A employs only onejoint 4404 connecting two links, 4402 and 4403, where a single resistivebend sensor 4401 is used to measure the angle 4405 between the links.The ends of the sensor are guided to lie tangent to the links, typicallyby directly affixing, enclosing a portion in a guiding channel orpocket, or some combination thereof. FIG. 44B presents a three-jointstructure 4406, comprising joints 4410, 4411 and 4412, where the ends ofresistive bend sensor 4407 are guided to lie tangent to terminal links4408 and 4409. Due to the properties of the sensor 4407, the individualangles of joints 4410, 4411 and 4412 are unimportant, whereas the sum ofthe angles 4413 is what is measured by the sensor.

[0167] FIGS. 45A-45D disclose a “cascade sensor” and its electricalconstruction. FIG. 45A is the side view of a single resistive bendsensor 4500 and 4518, comprising two variable-resistance strain-sensingelements 4505 and 4506 combined back to back. In the drawing, theseparation between the two elements is shown exaggerated to demonstratethe back-to-back construction. One example of a variable-resistancestrain-sensing element is a strain gage, which is what is shown here,with resistive metal grid 4517 attached to plastic backing 4507. Detailsof a sensor such as sensor 4518 and its electrical instrumentationcircuitry is provided by U.S. Pat. Nos. 5,047,952 and 5,280,265, thecontents of which is incorporated herein by reference. The electricalleads to sensor 4518 are wires 4508. An equivalent bend sensor to sensor4500 is cascade sensor 4501.

[0168] Cascade sensor 4501 comprises individual resistive bend sensors4502, 4503 and 4504 placed such that there is minimal overlap of thesensor ends, but that the ends of the neighboring sensors have paralleltangents. In the figure, three sensors are shown, however, anyconvenient number of sensors may be used. Since each resistive bendsensor measures the angle between the tangents at its ends, the sum ofthe signals of the individual sensors of such a cascade provides the sumof the angles. The signals from each sensor may be sensed individuallyand then summed, or alternatively, the signals may be summedelectrically by wiring the sensors as shown in FIG. 45D. When wired asshown in FIG. 45D, a cascade sensor results with the same performanceand characteristics as the single long monolithic sensor 4500 and 4518as shown in FIG. 45C. The leads 4516 of the cascaded sensor 4519correspond to the leads 4508 of the single long sensor 4518, and may beused equivalently in an electrical circuit.

[0169]FIG. 46 shows a shoulder sensor employing a long link-jointassembly 4600 comprising many joints, 4603, 4606, 4607, 4608 and 4609,with associated joint sensors. The particular kinematic arrangement ofthe links and joints may vary without deviating from the intended scopeof this invention. A particular useful kinematic arrangement is providedhere. The ends of the link-joint assembly 4602 and 4610 are secured onopposite sides of the human shoulder joint. Typically, one end of theassembly 4610 is secured to the humerus (biceps) 4611 and the other end4602 is secured to the upper back region, near the thoracic region 4601.The method of securing is typically done by strapping the assembly endto the body, or attaching the assembly end to a portion of an elasticbody covering, such as a Lycra suit. The joint angles may be sensed withresistive bend sensors, and may also be sensed using another convenientgoniometer, such as a Hall-effect sensor, an optical encoder, apotentiometer, a resolver, and the like. When a set comprising multipleneighboring joints have parallel axes, and when only the angle at theends of the set of joints is necessary, the angle may be determinedusing a single long sensor or a cascade sensor, such as shown in FIGS.45A-45D. In FIG. 46, joints 4606 form such a candidate set, joints 4607form a candidate set, joints 4608 form a candidate set and joints 4609form a candidate set of joints, whereby a long sensor may be used.

[0170]FIG. 47 provides another useful arrangement 4700 of links andjoints, to produce a canonical building block which is capable ofmeasuring any of the three possible spatial orientations of one end ofthe arrangement with respect to the other end, while allowing the threespatial translations of one end relative to the other. If a single longsensor 4709 is used, the translations cannot be measured. If there is aseparate goniometer, e.g., a resistive bend sensor, Hall-effect sensor,encoder, potentiometer, and the like, associated with each of the sixjoints, the three translations can be determined. In particular, thisstructure 4700 is useful since it allows relative translation of itsends using only revolute joints, since prismatic joints often havefriction and can bind. There are also conveniences when only goniometersneed to be used to make all measurements of a sensing device, and it canbe difficult and expensive to accurately measure prismatic elongations.The canonical structure 4700 shown in FIG. 47 may use resistive bendsensors to measure the joint angles. The structure comprises one axialjoint 4701, with associated sensor 4703, connected to one vertical joint4704, with associated sensor 4705, connected to a series of three joints4706, 4707 and 4708, with single associated sensor (or cascade sensor)4709, further connected to joint 4710, with associated sensor 4712. Theends of this arrangement 4700 are shown attached at one end to the femur(thigh) 4702 and at the other end to the pelvis 4711.

[0171]FIG. 48 shows repeated use of the canonical sensing arrangement4700 of six joints. In FIG. 48, canonical sensor 4700 is used as sensingdevice 4800 to measure the hip angle, used as sensing device 4801 tomeasure the lumbar region of the back, used as sensing device 4802 tomeasure the thoracic region of the back, used as sensing device 4803 tomeasure the neck, and used as sensing device 4804 to measure a portionof the shoulder. Obviously, the canonical sensing assembly 4700 may beused as convenient, where only some typical regions of use are shownhere. When used to measure the hip, ends 4805 and 4807 of the sensingdevice 4800 are secured to body portions 4806 and 4808, respectively;when used to measure the lumbar region, ends 4809 and 4811 are securedto body portions 4810 and 4812; when used to measure the thoracicregion, ends 4813 and 4814 are secured to body portions 4812 and 4815;when used to measure the neck, ends 4816 and 4817 are secured to bodyportions 4815 and 4818.

[0172]FIG. 49 provides a backside joint-link schematic view of a usefulembodiment of a body sensing system. A link-joint shoulder-sensingstructure 4900 is secured at its ends to support mounts 4908 and 4903located on or near the upper back, e.g., thoracic region, and thehumerus of the arm, respectively. As shown, the joints of theshoulder-sensing structure are grouped into neighboring joint sets sosingle long monolithic or cascaded sensors may be employed if desired.Three joints 4907 form a long-sensor-candidate joint set, which isconnected to single joint 4906, which is connected to a four-joint set4905, which is connected to a single joint 4904, which is connected to aseven-joint set 4902. The common axis orientation of joints 4907 isnominally in the plane of the back; the axis of joint 4906 is nominallyperpendicular to the back; the common axis orientation of joints 4905 isnominally in the plane of the back; the axis of rotation for joint 4904is along the long axis of the body; and the common axis orientation forjoint 4902 is in the plane of the humerus and forearm when the elbow isflexed.

[0173] The link-joint device 4901 for measuring the hip is attached tomount 4914 and mount 4912 which are secured to the thigh and pelvisregions of the body, respectively. The device 4901 comprises joint set4918, with common axis normal to the plane of the thigh and calve whenthe knee is bent; joint set 4917, with common axis lying nominally inthe plane of the thigh and calve; and joint set 4916, with common axisnominally parallel to the long axis of the femur.

[0174] Devices 4900 and 4901 allow unrestricted range of motion of theassociated body joint. When long or cascaded sensors are used to measurethe angle of a joint set, only orientation of the associated limb can bedetermined. Using knowledge of the kinematics of the human body, andusing inverse kinematic mathematical techniques, the joint angles of thebody joints can be resolved.

[0175]FIG. 49 shows the use of single degree-of-freedom resistive bendsensors to measure single degree-of-freedom joints, such as the elbow4910 with sensor 4909, knee 4920 with bend sensor 4919 and ankle 4924with sensor 4921 on the instep 4922 and with sensor 4923 on the side ofthe ankle. It is also convenient to use the single-axis bend sensors tomeasure the angles of the joints of the hand. A CyberGlove by VirtualTechnologies, Inc. of Palo Alto, Calif. provides such sensing means inan elastic glove.

[0176] FIGS. 50A-50D provide a device 5000 for measuring axial rotationof a human body part such as the forearm (FIGS. 50B and 50C), waist,head and leg (FIG. 50D). Device 5000 comprises a flexible transmissioncable or flexible shaft 5001 which is flexible in bending, but stiff intorsion. That is, it is able to transmit torsion. Such cables are oftenused for flexible couplings and drive shafts, such as may be used forradio-controlled boats. One end 5005 of cable 5001 is attached to afirst body part, while the other end of the cable rotates relative tohousing 5002, which is secured on a second body part which is capable ofrotating relative to the first body part. A goniometer is associatedwith housing 5002 which can determine the rotation of the cable. Typicalgoniometers include resistive bend sensors, Hall-effect sensors, opticalencoders, potentiometers, resolvers, and the like. Since the cable isflexible, it is comfortable and can bend around joints which are notintended to affect the rotation of the cable, while still measuring therotation of a body part due to the axial transmission of the rotationvia the cable.

[0177] As shown in FIG. 50B, one end 5007 of the cable 5006 is securedto the wrist of an arm by strap 5008, while the other end 5009 of thecable is attached to the arm, for instance near the elbow, by strap5010. Either end 5007 or 5009 may include the goniometer. If thegoniometer adds weight or bulk to the end of the cable, that end istypically placed nearer the torso for better support and to reduce theeffect of inertia. FIG. 50C shows another useful embodiment where oneend 5014 of the cable 5011 is attached via strap 5015 to the humerus.The other end 5012 is again attached near the wrist with strap 5013.FIG. 50D shows a useful embodiment where one end 5017 of cable 5016 isattached by strap 5018 to the foot, and the other end 5019 is attachedto the waist by securing means 5020. As mentioned above, either end maycontain a goniometer for measuring the rotation of the cable. Ifpreferred, a goniometer may be employed in both ends of the cablestructure.

[0178] This flexible-cable sensing technique allows sensing of relativerotation (nominally axial to the cable or flexible shaft) between twobody links that can also articulate relative to each other about an axisother than the cable axis. The flexible-cable sensor 5000 may be used tomeasure rotation of inanimate machines or objects, and animate bodiesother than human bodies.

[0179]FIG. 51 is similar to FIG. 48, but is also shows the use of theflexible-cable sensor for measuring the forearm rotation and the legrotation. Cable 5109 is connected by ends 5111 and 5110 to the humerusand wrist regions, respectively; cable 5112 is connected by ends 5113and 5114 to the foot and pelvis, respectively; canonical six-jointsensing assembly 5100 is connected at its ends to securing mount 5103and 5104; assembly 5101 is connected to mount 5104 and 5105; assembly5102 is connected to mount 5105 and 5106. Flat, flexible resistive bendsensors 5107 and 5108 are placed in functional relation to the shoulderto measure the sterno-clavicular elevation (pitch) and azimuth (yaw),respectively. Such a sensing assembly can measure the movement of thelumbar, thoracic and neck regions of the back, the shoulder and hipmovements and the forearm and leg rotations. Obviously, other sensorsmay be conveniently used to measure other desired degrees of freedom ofthe human body.

[0180]FIG. 52 provides another way to measure the rotation of theforearm using axial revolute joint 5209 as part of assembly 5200. Herejoint 5201 is secured to mount 5213 which is secured to the torso,typically by straps or elastic material. Joint set 5202, measured byresistive bend sensor 5203 is connected to joint 5201 and to axial joint5204. Joint 5204 is secured at location 5205, which is further connectedto axial joint 5206. Joint 5206 is connected to joint set 5207 andsensed by sensor 5208. Set 5207 is connected to axial revolute joint5209 which is connected to wrist abduction joint 5210 which is connectedto wrist flexion joint 5211 which is terminated on the hand region bysecuring means 5212. As such, the axial rotation of the forearm ismeasured by axial joint 5209. Various modification may be made to thekinematic structure of this mechanism without departing from theintended scope of the subject invention.

[0181]FIG. 53A shows the construction of a resistive bend sensor 5300comprising four variable resistance sensing elements, such as a straingage. The elements 5301 and 5301 are located on one side of flexible,incompressible backing 5305, while elements 5303 and 5304 are located onthe other side of backing 5306, where both sides are combined back toback, typically by adhering or monolithic construction, the resultingsensor provides in a single unit, all elements necessary for afully-balanced Wheatstone bridge circuit. Thus, the sensor is veryinsensitive to temperature fluctuations, electrical noise, changes inthe mechanical properties of the materials, and the like. The sensorassembly also doubles the sensing signal over the case when only asingle sensing element on each backing is used, and aconstant-resistance reference half-bridge is employed. In FIG. 53A, thetwo sides of the sensor are shown apart so the construction of thesensor can be more easily demonstrated. The “top” and “bottom” elementgrids may have solder tabs or though-holes aligned to make leadconductor attachment more convenient, e.g., where a single solderingstep is needed. FIG. 53B provides the electrical connections of thesensing elements in a Wheatstone circuit, where differential amplifier5307 provides an analog output proportional to the angle between thetangents at the ends of the sensor 5300. The bridge circuit hasexcitation voltage 5308.

[0182]FIGS. 54A and 54B provide an axial sensors constructed using aflexible resistive strain-sensing bend sensor. Axial sensor 5400comprises rotary portion 5401 which rotates about axis 5414 relative tohousing 5402. Bend sensor 5403 is connected at end 5404 to rotaryportion 5401, where sensor end 5406 is free to slide in guiding channel5407. Sensor wires 5405 may exit the assembly in any convenient manner,such as along the direction of axis 5414. Since the bend sensor measuresthe angle between the tangents at its ends, as rotary portion 5401rotates relative to housing 5402, the sensor signal changesproportionally.

[0183]FIG. 54B provides another embodiment to provide axial measurement.Rotary component 5408 rotates relative to housing 5409 about axis 5415.End 5411 of resistive bend sensor 5412 is affixed to rotary component5408, while end 5413 is affixed to housing 5410. The amount of “slack”in the sensor determines how many degrees of rotation can be sensed.

[0184]FIG. 55 provides an embodiment 5500 whereby three degrees offreedom of orientation between two links 5501 and 5502 can be measured.Link 5501 rotates relative to housing 5507, where sensor 5504, shown onthe bottom surface, measures the rotary angle. Cylinder 5503 is attachedto housing 5507 and rotates relative to housing 5508, where sensor 5506measures the angle of rotation. Housing 5508 is attached to housing 5509relative to which link 5502 rotates, which rotation is measured bysensor 5505. This structure is shown as such to provide a functionaldescription of how to create a 3-degree-of-freedom orientation sensorfrom rotary joints, and where the axes of the rotary joints all convergeat a single point, i.e., a “ball joint” is effectively created.Modifications may be made to this design as convenient.

[0185]FIG. 56 shows a variety of body-function sensing and feedbackdevices that may be used with a body-sensing apparatus 5618 as providedby the subject invention. In particular, a useful feedback device is avibro-tactile element 5600, similar to a pager motor, which may beplaced at any convenient location about the body and programmed to adesirable frequency of vibration by a control program. A usefulbody-function-sensing element is an EMG 5601 sensor, so muscleelectrical activity may be correlated to resulting joint motion. Anotheruseful parameter to be measured is ground reaction force as measuredoptionally by force/presure pads 5604 on the bottom of a foot. Othersensing and feedback elements associated with the apparatus 5618 includea force/pressure-sensing platform 5605, a data-logging communicationmodule and local computer 5616, a body-position and orientation sensor5617 (e.g., inertial or electromagnetic, optical or ultrasonic), EKGsensor 5602, microphone 5606, respiration sensor 5607, earphone 5608,EEG sensor 5609 attached to headband 5610 or to hood 5611 of suit, EOGsensor 5612, eye tracker and/or facial expression monitor 5613 andforce/pressure/contact sensors 5603 on hands. Other elements included inthe figure include a golf ball 5619, golf club 5614 and instrumentedglove 5615, such as a CyberGlove. Such a body-sensing and feedback suitfinds utility in sports analysis, virtual reality, motion capture,biomechanics, and the like.

[0186] FIGS. 57A-57C add angle sensors and plates to the axial rotationsensor of FIG. 50. Plates 5704 and 5705, which are flexible about theirminimum-moment-of-inertia axis, and resistant to bending about the othertwo axes, are affixed to the flexible transmission cable 5701. The cablehas ends 5702 and 5703, at least one of which has a goniometer tomeasure the relative rotation of the ends of the cable. As shown in FIG.57C, each plate 5710 is affixed only at one end 5711 to the cable 5709,whereas the other end of the plate is allowed to slide relative to thecable, typically by employing cable loops 5712. The plates act toprotect the flexible resistive bend sensors associated with each plate.Each plate has a guiding means associated with it to guide theassociated sensor. FIG. 57B shows a simplified discrete link-jointstructure model of the cable sensor of FIG. 57A, where the sensors andplates are positioned alternating at 90 degrees to each other. Tocalculate the orientation of the endpoints 5702 and 5703 of the cable,it is typically assumed that the cable flexes with a constant arc overthe region of each bend sensor. For this configuration, each bend sensorshould be sensed independently of the others. All sensors along thecable, may, however, be attached to its neighbor on a flexible circuitsubstrate, such as is provided in FIGS. 42A and 42B.

[0187] FIGS. 58A-58C provide various specialty joint-sensing devices.FIG. 58A provides a knee-angle monitor 5800 comprising body mountingstrap 5801, which may be a commercial elastic knee brace, a resistivebend sensor 5802 in a guide on strap 5801 which holds the ends of thesensor tangent to the thigh and shin. A monitor 5803 may be attached todevice 5800, or may be located in convenient proximity thereto, ormounted near the waist in a larger monitor pack 5804. The monitor maycalculate the joint angle and may perform various functions such as viaan LCD screen or voice synthesizer it may inform the wearer of variousstates of their joint. The monitor may have LEDs to provide information,and may provide such joint information and functions as average angle,minimum and maximum angles, reset, start/stop data acquisition,repetition rate, and the like. In a rehabilitation function, the monitormay request that the wearer perform range-of-motion exercises andencourage improved performance based on desired movements. The monitormay also warn the wearer if an acceptable joint ranges were beingexceeded, for instance using a tone or buzz. An ankle monitoring device5805 is also shown in FIG. 58A, where ankle strap 5807 comprises asensor guide to guide sensor 5806 to measure the angle of flexion of theankle. The ankle strap may be similar to a commercial ankle brace. Theknee and ankle monitoring systems may be used independently or together,or with other joint sensing devices.

[0188]FIG. 58B provides an elbow-sensing device 5808, similar in natureto the knee and ankle-sensing devices of FIG. 58A. Elbow-sensing device5808 comprises an elbow strap 5810 with a sensor guide to guide theresistive bend sensor 5809 over the elbow joint, keeping the tangents atthe ends of the sensor tangent to the humerus and forearm. A monitor5811 may also be used. FIG. 58C provides a wrist-sensing device 5812comprising two wrist sensors 5813 for measuring wrist flexion andabduction. The sensors are guided along the wrist by guides in handstrap 5814. A monitor 5815 may be used similarly to the previousspecialty joint sensors.

[0189] All publications and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication or patent application was specificallyand individually indicated to be incorporated by reference.

[0190] The invention now being fully described, it will be apparent toone of ordinary skill in the art that many changes and modifications canbe made thereto without departing from the spirit or scope of theappended claims.

What is claimed is:
 1. An apparatus for measuring the relative spatialplacement of two terminal links, said apparatus connected by links andrevolute joints and comprising: at least one of the following sensingdevices: a first sensing device comprising a long resistive bend sensorextending over multiple joints with parallel axes from terminal link toterminal link; and a second sensing device comprising multiple shortresistive bend sensors and multiple links and revolute joints andterminating in terminal links, with each sensor measuring one revolutejoint angle; means for mounting said sensing device on said body parts;and means for receiving electrical signals from said sensing device;wherein said first sensing device provides a signal for the entire anglebetween said terminal links and said second sensing device provides asignal such that the relative position and orientation of said terminallinks can be determined using forward kinematics.
 2. An apparatus formeasuring angles of portions of a human body, said portions comprisingat least one of the shoulder and the hip, said apparatus comprising: atleast one of the following sensing devices: a first sensing devicecomprising a long resistive bend sensor extending over multiple jointswith parallel axes from terminal link to terminal link; and a secondsensing device comprising multiple short resistive bend sensors andmultiple links and revolute joints and terminating in terminal links,with each sensor measuring one revolute joint angle; for the shoulder,means for securing said sensing device to said human body to measure theangle of the humerus in relation to the torso, whereby one terminal linkmoves with said humerus and the other terminal link moves with saidtorso; for the hip, means for securing said sensing device to said humanbody to measure the angle of the femur in relation to the torso, wherebyone terminal link moves with said femur and the other terminal linkmoves with said torso; a data processor for receiving electrical signalsfrom said sensing devices and determining angles from said signals. 3.An apparatus according to claim 2, comprising sensing devices formeasuring both said shoulder and said hip.
 4. An apparatus according toclaim 2, further comprising: at least one resistive bend sensor formeasuring an elbow, wrist, knee or ankle body part; means for mountingsaid resistive bend sensor in angle-measuring relation to said elbow,wrist, knee or ankle body part.
 5. An apparatus for measuring angles ofportions of a human body, said portions comprising at least one of theshoulder and the hip, said apparatus comprising: at least one prismaticsensing device for measuring said angle in relation to at least one ofsaid shoulder and hip; optionally at least one of the following revolutesensing devices: a first sensing device comprising a long resistive bendsensor extending over multiple joints with parallel axes from terminallink to terminal link; and a second sensing device comprising multipleshort resistive bend sensors and multiple links and revolute joints andterminating in terminal links, with each sensor measuring one revolutejoint angle; at least one resistive bend sensor for measuring an elbow,wrist, knee or ankle body part; means for mounting said resistive bendsensor in angle-measuring relation to said elbow, wrist, knee or anklebody part; for the shoulder, means for securing said sensing device tosaid human body to measure the angle of the humerus in relation to thetorso, whereby one terminal link moves with said humerus and the otherterminal link moves with said torso; for the hip, means for securingsaid sensing device to said human body to measure the angle of the femurin relation to the torso, whereby one terminal link moves with saidfemur and the other terminal link moves with said torso; a dataprocessor for receiving electrical signals from said sensing devices andsensors and determining angles from said signals.
 6. An apparatus formeasuring the orientation of two body parts having up to three degreesof freedom of orientation and position relative to each other, saiddevice comprising: at least two revolute sensing devices connectedtogether: wherein said sensing devices are selected from: a firstsensing device comprising a long resistive bend sensor extending overmultiple joints with parallel axes; and a second sensing devicecomprising multiple short resistive bend sensors and multiple links andrevolute joints, with each sensor measuring one revolute joint angle;where when said second sensing device is absent, at least two of saidfirst sensing devices articulate in different planes; first and secondterminal links at the ends of said apparatus; means for securing saidterminal links to said body parts; a data processor for receivingelectrical signals from said sensing devices and determining orientationfrom said signals, and when solely said second sensing device is used,further determining position from said signals.
 7. An apparatusaccording to claim 6, wherein said second sensing device is absent, saidapparatus further comprising at least one revolute joint measured by ashort resistive bend sensor.
 8. An apparatus according to claim 6,wherein said body parts comprise the thoracic region of the spine andhumerus.
 9. An apparatus according to claim 6, wherein said body partscomprises the pelvis and the femur.
 10. An apparatus comprising aplurality of links and at least one revolute joint, said apparatuscomprising: assembled units, where each unit comprises a body with firstand second components secured together, said units comprising linkingmeans for linking a series of units and a passageway for receiving asensor extending through said assembled units, said units formed byjoining face-to-face said first and second components, each of saidcomponents comprising a post at one end extending outward, where the twoposts are spaced apart when said units are joined to define a portion ofsaid passageway, an orofice at the other end for receiving a post of anadjoining unit, and one half of said passageway; a sensor extendingthrough said passageway; and means for electrical connection to saidsensor.
 11. A method for measuring angles of portions of a human bodywherein at least one of said portions comprising at least one of theshoulder and the hip, comprising: providing a sensing device selectedfrom the group of sensing devices onsisting of: (i) a first sensingdevice including a long resistive bend sensor extending over multiplejoints with parallel axes from terminal link to terminal link; (ii) asecond sensing device including multiple short resistive bend sensorsand multiple links and revolute joints and terminating in terminallinks, with each sensor measuring one revolute joint angle; for theshoulder, securing said sensing device to said human body proximate theshoulder; and measuring the angle of the humerus in relation to thetorso such that one terminal link moves with said humerus and the otherterminal link moves with said torso; for the hip, securing said sensingdevice to said human body; and measuring the angle of the femur inrelation to the torso, such that one terminal link moves with said femurand the other terminal link moves with said torso; and receivingelectrical signals from said sensing devices and processing said signalsin a computer processor to determine angles from said signals.